I was flying a Bell 47 Sioux with the Royal Marines in Aden in 1967. Tasked to take a photographer to a weapons find high on a jebel. Hovered over a slope near the edge of a very steep drop to check if we could land when there was a loud crack, the cyclic went loose, and we turned upside down! Can't remember getting out, but we both did, unharmed. The only thing that stopped us going over the edge was one of the main rotor blades stopped, pointing down the slope and the wreck was swaying on that! Frightened? I still have nightmares!!